Abstract The perfluoronitrosocycloalkanes, heptafluoronitrosocyclobutane and nonafluoronitrosocyclopentane, are convenient precursors to a family of new perfluorocycloalkyl(aryl) diazenes. With aniline and o -aminobenzamide, CF 2 (CF 2 ) x C FNN C(CH) 4 C H and CF 2 (CF 2 ) x C FNN C(CH) 4 C C(O)NH 2 (x = 2,3) are formed. Additionally, heptafluoronitrosocyclobutane gives CF 2 (CF 2 ) 2 C FNN CCFCFCHCFC F and CF 2 (CF 2 ) 2 C FNN C(CH) 4 C NH 2 with 2,3,5,6-tetrafluoroaniline and o -phenylenediamine